As Nick stares down his report and the list of 35 vocabulary words that Mrs. Granger assigned, he pouts about having to do homework on such a beautiful day. Mr. Allen and Mrs. Allen insist that their children complete their homework first thing after school. They were thrilled when their oldest son James wrote home from college and thanked them for this rule, saying that because they taught him to put homework first, his grades were impeccable. The rule has never bothered Nick in the past, as he hasn't had much homework. Now, however, he recognizes that those idyllic days are over.
The realization that because Nick is growing up, he's going to have to follow new rules suggests that as Nick moves towards maturity, the power structures around him are going to change and he'll have to renegotiate where he stands. This mirrors what's going on in Mrs. Granger's class as well, as fifth grade is looking to be the year that Nick will learn that he can't just thwart power systems willy-nilly.
Nick begins by looking up the vocabulary words in the dictionary, which takes him an hour. He can hear a baseball game outside, but he knows he has to finish his report first. Nick finds an introduction in the front of his dictionary called "Words and their Origins." He's thrilled to have found an easy source for his report, but he soon finds that the article is unintelligible.
Were Mrs. Granger around, she'd likely say that Nick's inability to understand the introduction is the entire reason she assigns vocabulary words in the first place. This continues to show that Mrs. Granger is teaching kids tools they can use to understand their world, not just giving them arbitrary assignments.
Nick heads downstairs to the family room, finds the set of children's encyclopedias, and looks up "dictionary." He reads the entry in the adult encyclopedia as well, though he only understands about half of what he reads. Nick groans, thinking that it'll be impossible to come up with three minutes' worth of material. Then, he has one of his ideas and decides to make the report fun.
Note that though Nick doesn't understand what he reads, he still apparently knows enough to presumably thwart Mrs. Granger. This shows that even if Nick isn't able to fully understand the encyclopedia entries, he's able to think outside the box and use what he does understand to his advantage.